Issue #118 wanted better TOR support, now Avatar URLs are not stored

There was no reason to store the generated Avatar URLs because it's so
cheap to generate them on the fly.

plugins/TwitterBridge/lib/twitterimport.php

@@ -366,7 +366,6 @@ class TwitterImport
         $avatar->original   = 1; // this is an original/"uploaded" avatar
         $avatar->mediatype  = $mediatype;
         $avatar->filename   = $filename;
-        $avatar->url        = Avatar::url($filename);
         $avatar->width      = $this->avatarsize;
         $avatar->height     = $this->avatarsize;